I ran the test again with fan set to 100% but the problem persists.this is normally due to thermal limits. notice that the temps stay maxed out almost 100% of the run. this tells you that the card is likely throttling due to hitting thermal limits.
It does not have any custom bios or settings.if it's not thermals, then i'm not sure. i actually have an older system with an r9-270 installed. weaker CPU in mine than the i7 you have but i have one also.
when i get home later today i'll run that benchmark and see what happens. i don't normally run them and have to install this to do it but i'll give it a shot just to see.
might be normal behavior you're seeing, might not be. we'll see what my 270 does with it. though i'm not expecting much on a 4k benchmark with such a low end GPU.
if there are custom settings you are running or anything other than the normal run, please let me know so i can match it when i run it later.